The very metal-poor local dwarf galaxies

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Дата изменения: Mon Feb 18 13:29:39 2008
Дата индексирования: Tue Oct 2 02:51:06 2012
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The very metal-poor local dwarf galaxies - the analogs of primordial galaxies in young Universe

This is RFBR supported project for years 2006-2008 under grant 06-02-16617a

The goal of this project is the study of the properties of the local eXtremely Metal-Deficient (XMD) dwarf galaxies. The properties of massive stars and gas in these objects best approximate the properties that are expected for young galaxies in the early (z=5-7) Universe. The latter, however, are too faint and "compact" to study them even with the largest telescopes. Therefore the observational study of their rare analogs in the nearby Universe is a good complementary channel for understanding physical processes in the primordial galaxies. Besides, there exist several "nearby" objects (similar to I Zw 18), in which the careful search for old stellar population gave negative results and placed only upper limits on its mass. Such objects are the full analogs of young galaxies in the early Universe. Their study can give the most valuable information on the early galaxy evolution.

We plan to study the kinematics and density distribution of neutral and ionized gas, in particular, in galaxies with indication of interaction; their relation to star-forming regions and young star clusters; the heavy element composition and their distribution on galaxy body; to study the colours of outer parts of these galaxies and give the age estimates of the oldest visible stars; to estimate the relative numbers of WR stars in XMD galaxies and compare them with modern models of massive star evolution predictions for stars with very low metallicities.

Particular tasks for this period include:

The increase of the volume of XMD galaxy sample with the help of high S/N ratio spectroscopy of preselected candidates from HSS, HSS-LM and SDSS.

The estimates of XMD galaxies' ages based on the colours of their outer regions on observations in BVRI and JHK, complemented with images in H-alpha to account for possible contribution of nebular emission.

High S/N ratio long-slit spectrophotometry of selected XMD galaxies to address the issues of heavy element patterns and chemical evolution, to measure WR star features and to examine possible metallicity inhomogenieties along galaxy bodies.

Observational study of integrated HI parameters in a large sample of XMD galaxies. Statistical analysis of HI in XMD galaxies along with other global parameters and in comparison to more common late-type low-mass galaxies.

The study of moprphology, structure and kinematics of HI in a subgroup of about a dozen XMD galaxies based on the observations with GMRT radiotelescope (India), in collaboration with colleagues in NCRA (Pune).

The detailed multiwavelength study of several XMD galaxies with clear evidences of interaction/merger as an opportunity to approach the processes typical of star formation in the early Universe, when galaxies both were very metal-poor and experienced frequent interactions (due to much higher galaxy densities) and induced starbursts. This includes both HI and Ha (with IFP) maps/velocity fields, deep imaging in optics/NIR and abundance spatial distribution picture.

Some preliminary results for the year 2006